Ecogenetics of Schistosoma japonicum transmission in China. The long-term objectives are to combine remote sensing (RS) and geographic information systems (GIS) with ecological and population data 1) to assess the ecological conditions in three large areas below the Three Gorges Dam and one large area above the Three Gorges Lake that provide suitable habitats for Oncomelania hupensis snails and the transmission of Schistosoma japonicum, 2) to assess short and long-term seasonal environmental changes as they impact snail habitat and snail population structure, including infectivity patterns, in these four significantly different highly endemic areas, 3) to assess land-cover changes in the targeted areas caused by human activity that increase the risk of schistosome transmission. A major goal of these studies is to create surveillance plans that target areas of high risk involving four discretely different modes of schistosome transmission before the completion of filling of the Three Gorges Lake (basic benchmarking) and after the filling of the lake (causing major shifts to new ecologies). Unlike the studies of Cross et al. (1984,1996) and Malone et al. (1994, 1997) that focused on correlating snail habitat with disease prevalence, this proposal builds on the work of Spear et al. (1999) and Seto (2000) in using a twotiered RS classification that explicitly focuses on distinguishing between snail habitat and non-habitat. The focus on identifying temporal changes in snail habitat and the prediction of the location of local Optimal Transmission Sites (OTS) is the goal of public health prevention. This enables rapid identification of emerging snail habitat with ensuing control of snail populations before the onset of disease. We plan to confirm that preliminary analyses in Sichuan of satellite and ground data show that the habitat of Oncomelania hupensis spp can be statistically identified from Landsat Thennatic Mapper (TM) imagery .This habitat classification will be applied to four highly distant areas involving four different modes of schistosome transmission. We will make this identification more precise by supplementing satellite data with landscape features and ecological variables derived from ground data available. An ecological interpretation of the statistical classification will be developed. We plan to couple theses technologies to land-based studies to determine the scope and impact of temporal environmental changes on snail habitat benchmark sites and snail/parasite populations. Our concerns here are on temporal changes over a number of years impacting habitats suitable for snails, snail density and infection rates.